Recovery of hydrogen fluoride



RECOVERY oF HYDROGEN FLUORIDE Filed Nov. 16, 1942 Paume Jau. i. i946 Louis f8. Kassel, Chicago, lil., assigner to Universal Oil Products Company,

A ration of Delaware Chicago, lll., a comv oppression November 1e, 1942, seria: No'. 465,696 l z claims. (ci. 26o-esas) Y A This invention relates to a method of recoverins free or uncom'bined hydrogen uoride from hydrocarbon mixtures containing hydrogen fluoride. lt is'more particularly concerned with a method oi' recovering hydrogen fluoride from admixture with substantially saturated hydrocarbons, e. g., the reaction products or unconverted reactants from a hydrogen iluoride alwlation process. v

In the catalytic alkylation of isoparafns with oleilns in the presence of a hydrogen iluoride catalyst. i. e., a catalyst whose essential active ingredient is hydrogen iluoride, the catalyst is not consumed to anyappreciable extent and may be recovered in substantial amounts as hereinafter described. Although the hydrogen iiuoride catalyst becomes .contaminated with organic contaminants and water duringy the procesathe used catalyst;I can be readily regenerated and purliled hydrogen fluoride can be recovered and returned to the alkylation zone.

Since hydrogen 'uoride is soluble to the extent of approximately l or 2% in the substantially saturated ablation reaction products, it is apparent that a small portion of hydrogen fluoride will be carried out of the reaction zone with the conversion products. In the process oi' my invention this dissolved hydrogen iluoride is recovered from the hydrocarbon reaction products and recycled to the reaction zone thereby eilectng a substantial economy ci' operation. ln previously proposed isoparamn-oleiin ellrylation processes employing catalysts such as concentrated sulfuric acid, the dissolved acid or acid bodies in the hydrocarbon reaction products have been removed by treatment with a neutralizing agent such as caustic soda, and the dissolved catalyst was thereby lost from the process.

' In one specific embodiment the present invention comprises a process for the recovery oi-iree hydrogen uoride fromV admixture with substantially saturated hydrocarbons which comprises extracting a substantial portion of the hydrogen uoride from said mixture with an aqueous. solutionot` hydrogen nuoride and iractlonatlng the resultant extract to seperate substantially anhydrous hydrogen fluoride there-- from.

Although the present method of recovering hydrogen uoride is particularly applicable to an slkylation process employing hydrogen iluo ride'as the catalyst, it is equally adaptable to appreciable amounts of uncombined-or free hy.

drogen fluoride are found in the. hydrocarbon y reaction products or any portion thereof.

The advantages and various applications ofmy process will become morev apparent in connection with the accompanying drawing which is a schematic now diagram of a hydrogen liucride alkylatlon process whereinl iscbutaneis reacted with oleins in the presence of hydrogen fluoride. y

Referring to the drawing, isobutane is introduced through line i into alkylation zone d.

vThis zone may comprise any convenient appef.

ratus or arrangement oi apparatus suitable for effecting intimate contact between the hydrocarbon reactants and the hydrogen iluoride catalyst, e. g., e. mechanically agitated reaction zone ora so-called "timertanlr wherein intimate contacting is obtained bymeans' of bai'iies, orifices. or iets. The oletinic reactants which may comprise normally gaseous oleins, normally liquid olefins or polymers, are introduced through time which is deilned as the yoluune oi' catalyst in thereaction zone divided by the hydrocarbon feed rate in volumes per minute. i space time ot' from about 5 to about 80 minutes will. ordinarily be employed. As is well-known in the alkylation art, it is desirable to maintain s substantial excess of isoparaillns over olens in the combined any .hydrocarbon 'conversion pross 'employing a l:hydrogen duende-containing catalyst wherein feed to the alkylation zone, e. g., from about 2:1 to about 10:1 or higher.

Although commercial "anhydrousi hydrogen huoride isl usually charged to the process, it is possible to have as much as about 10% oiwater present` in the' catalyst. Excessive dilution with water is undesirable, however, because -of the danger oi' corrosion and'because the alkylating activity or the catalyst diminishes with increas-` ing water content. Minor amounts of promoters such as boron trifiuoride may also be present in the hydrogen iluoride catalyst.

The mixture of catalyst and hydrocarbon reaction products passes through line 5 to separa- 4 tion sono l which ordinarily comprises a settling zone. The upper hydrocarbon layer containing dissolved hydrogen fluoride is withdrawn through line 'I for further treatment as hereinafter de is recycled through line Il to line 3 and thence into allsylation zone Ii. During the course of the reaction the hydrogen fluoride-catalyst tends to become contaminated with organic contaminants of a polymer-like nature and also with water. In order to prevent the excessive build-up of them materials, a portion of the used catalyst is directed through line into regeneration zone- 8 which may comprise a simple fractional distillation step. During the fractionation the hydrogen lfluoride-hydrocarbon complexes are broken down and free hydrogen iiuoride and water are distilled overhead. The organic contaminants may be removed through line I. The hydrogen uoride-water mixture (which in certain cases may also contain small amounts of dissolved light hydrocarbons) is withdrawn through line I I. A portion of this stream may be directed through lines I2 and I5 to line 9 and thence through line 3 to the alkylation zone. In order to prevent the build-up of water in the catalyst phase at least a' portion of the hydrogen fluoride-water stream is passed through line .Il to fractionation zone I3. In this zone substantially anhydrous hydrogen fluoride may be distilled overhead from a bottoms product comprising' hydrogen iiuoride and water having a higher water content than the charge to the fractionating column. 'I'he anhydrous hydrogen iiuoride is recovered through line I4 and returned to the alkylation zone through lines I5, 9, and 3.

The hydrogen fluoride-water mixture is removed as a bottoms product from fractionation zone I3 through line I6. This material may conviently comprise the so-called constant boiling 'mixture which.- at atmospheric pressure, will contain from about 35 to about 40 weight per cent of hydrogen fluoride. aqueous hydrogen fluoride stream is introduced through line I1 into extraction zone I8 wherein it is contacted with the hydrocarbon reaction products introduced by means of line 1. Additional amounts of hydrogen fluoride or water or both may be added to the solvent through line 21. Extraction zone I8 is ordinarily operated under liquid phase conditions at temperaturesof from about 50 to about 150 F.' and pressures of from about 50 to about 150 pounds per square inch. In certain cases it will be possible toyoperate outside of these conditions. The extraction zone may comprise any of .the well-known forms of contacting apparatus. e. g., a packed reaction zone or a bubble plate column. Under the conditions of operation the free hydrogen fluoride contained in the hydrocarbon rate a product of desired end Point. It will usually be desirable also tosubject the aikylote to an additional treating step for the removal of combined hydrogen fluoride, e. g., alkyl uorides which are .usually present in relatively smallA amounts. Normal butano may be removed through line 25.

Although my invention has been described in y connection with the removal of dissolved hydrogen fluoride from the total hydrocarbon reaction products priorto fractionation thereof, it will be apparent that the extraction method may be ap plied to any hydrocarbon stream containing free hydrogen fluoride. For example, the hydrocar' bon reaction products in line 'I may be subjected to a deisobutanization step wherein an overhead stream comprising isobutane, hydrogen fluoride, and propane or other light hydrocarbons is separated from a bottoms product comprising alkyla- This overhead stream of isobutane, propane, and hydrogen duoridefor any portion thereof, may then be subjected to an extraction step with a hydrogen uoride-water mixture in the manner ilii'hereinbefore described. iIt will be apparent t0 those skilled in the art that the fractionation of the hydrocarbon reaction products and the separation and recovery of dissolved hydrogen nuoride may be effected in a variety of ways, dependent upon the fractionation scheme chosen. In general, my invention contemplates the recovery of free hydrogen uoride from any hydrocarbon stream or streams in the process.

I claim as my invention:

l. A process for the recovery of dissolved h!- mixture of hydrogen fluoride and water whereby stream introduced through line 1 is extracted by the hydrogen fluoride-water mixture. The emriched extract is withdrawn through une le and charged through line I I to the fractionation zone Il whereinthe hydrogen fluoride thus recovered' may be separated and returnedto the alkylation zone. A hydrocarbon stream which in many cases will be'substantially free of dissolved hydrogen uorlde is removed through line 2l to fractionation sone 2 I.

In zone 2| the hydrocarbon products are fractionated to separate desired reaction products from unconverted reactants and undesired products. Unreacted isobutane is withdrawn through line 22 and isv preferably recycled through line 23 to alkylation zone l. Light gases such as propane are removed through line 26. Alkylation reaction products are withdrawn through line 24 and may to extract a substantial portion of the 'dissolved hydrogen fluoride from said hydrocarbon mixture and subjecting the resultant extract to fractionation to separate substantially anhydrous hydrogen fluoride.

2. In the alkylation of isoparaiilns with olefins in the presence of a hydrogen fluoride catalyst wherein th'e bulk of the used catalyst is separated from the' hydrocarbon reaction products in a settling zone, the improvement which comprises re-l moving dissolved 4hydrogen fluoride contained in said hydrocarbon reaction products by subjecting the latter In liquid phase to solvent extraction.

with a hydrogen fluoride-water mixture containing a major proportion of water.

3. The process of claim 2 wherein the .enriched extract from said solvent extraction step is fractionated for the recovery `oi' substantially anhydrous hydrogen fluoride which is returned to the alkylation step.

4. In a process for the alkylation of isoparafilns with olens in the presence of a hydrogen fluoride catalyst wherein the bulk of the used hy- 'l0 ous hydrogen iiuoride is fractionated to separate substantially anhydrous hydrogen fluoride froma constant boiling mixture of hydrogen fluoride and water, and said substantially anhydrous hydrogen fluoride is returned to the alkylation zone.

be subjected` t0 additional frctinationto Spa- 75 the improvement which comprises contacting said tion products and unconverted normal butane.

hydrocarbon reaction products in liquid phase with said constant boiling mixture from said fractionation step whereby to extract a. substantial amount of dissolved hydrogen uoride contain'ed in said hydrocarbon reaction products and supplying the resultant hydrogen fluoride enriched extract to said fractionation step.

5. A process for purifying a. hydrocarbon liquid containing dissolved hydrogen fluoride which comprises subjecting the hydrocarbon liquid t0 an extraction treatment with a solution comprising a major proportion of water and a minor proportion of hydrogen fluoride.

about 35 to about 40 weight per cent of hydrogen fluoride in water.

LOUIS S. KASSEL. 

